The present invention relates to an elbow or proximal radioulnar joint prosthesis. The elbow joint includes three bones—the humerus, which extends from the shoulder to the elbow, and the radius and ulna, which lie parallel to each other and form the forearm, which extends from the elbow to the wrist. Currently, when the proximal head (the upper end as seen in FIG. 1) of the radius bone is damaged or destroyed, the standard procedure is to excise the damaged portion of the radius and, if deemed necessary to insert a prosthesis into the radius bone to replace the radial head. This radial head replacement relies on the annular ligament to hold the radius in position as it did prior to the procedure. If this ligament is damaged as part of the incident which caused the damage to the radial head (such as a dislocation or a fracture of the radial head), which is typical, then the prosthesis may become dislocated from the proximal ulna and or humerus and unable to transmit any axial loads from the hand, via the forearm and the elbow to the humerus. As a result, the patient is not able to transmit axial loads from the radius to the humerus.